Hydrocarbon conversion with an acidic multimetallic catalytic composite

ABSTRACT

Hydrocarbons are converted by contacting them at hydrocarbon conversion conditions with an acidic multimetallic catalytic composite, comprising a combination of catalytically effective amounts of a platinum group component, a rhenium component, a tin component, a cobalt component, and a halogen component with a porous carrier material. The platinum group component, rhenium component, tin component, cobalt component, and halogen component are present in the multimetallic catalyst in amounts respectively, calculated on an elemental basis, corresponding to about 0.01 to about 2 wt. % platinum group metal, about 0.01 to about 2 wt. % rhenium, about 0.01 to about 5 wt. % tin, about 0.05 to about 5 wt. % cobalt, and about 0.1 to about 3.5 wt. % halogen. Moreover, these metallic components are uniformly dispersed throughout the porous carrier material in carefully controlled oxidation states such that substantially all of the platinum group metal is present therein in the elemental metallic state, substantially all of the cobalt and rhenium components are present in the corresponding elemental metallic state or in a state which is reducible to the corresponding elemental metallic state under hydrocarbon conversion conditions or in a mixture of these states, while substantially all of the tin is present therein in an oxidation state above that of the elemental metal. A specific example of the type of hydrocarbon conversion process disclosed is a process for the catalytic reforming of a low-octane gasoline fraction wherein the gasoline fraction and a hydrogen stream are contacted with the acidic multimetallic catalyst disclosed herein at reforming conditions.

The subject of the present invention is a novel acidic multimetaliccatalytic composite which has exceptional activity and resistance todeactivation when employed in a hydrocarbon conversion process thatrequires a catalyst having both a hydrogenation-dehydrogenation functionand a carbonium ion-forming function. More precisely, the presentinvention involves a novel dual-function acidic multimetallic catalyticcomposite which, quite surprisingly, enables substantial improvements inhydrocarbon conversion processes that have traditionally used adual-function catalyst. In another aspect, the present inventioncomprehends the improved processes that are produced by the use of acatalytic composite comprising a combination of catalytically effectiveamounts of a platinum group component, a rhenium component, a cobaltcomponent, a tin component, and a halogen component with a porouscarrier material; specifically, an improved reforming process whichutilizes the subject catalyst to improve activity, selectivity, andstability characteristics.

Composites having a hydrogenation-dehydrogenation function and acarbonium ion-forming function are widely used today as catalysts inmany industries, such as the petroleum and petrochemical industry, toaccelerate a wide spectrum of hydrocarbon conversion reactions.Generally, the carbonium ion-forming function is thought to beassociated with an acid-acting material of the porous, adsorptive,refractory oxide type which is typically utilized as the support orcarrier for a heavy metal component such as the metals or compounds ofmetals of Groups V through VIII of the Periodic Table to which aregenerally attributed the hydrogenation-dehydrogenation function.

These catalytic composites are used to accelerate a wide variety ofhydrocarbon conversion reactions such as hydrocracking, hydrogenolysis,isomerization, dehydrogenation, hydrogenation, desulfurization,cyclization, polymerization, alkylation, cracking, hydroisomerization,dealkylation, transalkylation, etc. In many cases, the commercialapplications of these catalysts are in processes where more than one ofthe reactions are proceeding simultaneously. An example of this type ofprocess is reforming wherein a hydrocarbon feedstream containingparaffins and naphthenes is subjected to conditions which promotedehydrogenation of naphthenes to aromatics, dehydrocyclization ofparaffins to aromatics, isomerization of paraffins and naphthenes,hydrocracking and hydrogenolysis of napthenes and paraffins and the likereactions, to produce an octane-rich or aromatic-rich product stream.Another example is a hydrocracking process wherein catalysts of thistype are utilized to effect selective hydrogenation and cracking of highmolecular weight unsaturated materials, selective hydrocracking of highmolecular weight materials, and other like reactions, to produce agenerally lower boiling, more valuable output stream. Yet anotherexample is a hydroisomerization process wherein a hydrocarbon fractionwhich is relatively rich in straight-chain paraffin compounds iscontacted with a dual-function catalyst to produce an output stream richin isoparaffin compounds.

Regardless of the reaction involved or the particular process involved,it is of critical importance that the dual-function catalyst exhibit notonly the capability to initially perform its specified functions, butalso that it hss the capability to perform them satisfactorily forprolonged periods of time. The analytical terms used in the art tomeasure how well a particular catalyst performs its intended functionsin a particular hydrocarbon reaction environment are activity,selectivity and stability. And for purposes of discussion here, theseterms are conveniently defined for a given charge stock as follows: (1)activity is a measure of the catalyst's ability to convert hydrocarbonreactants into products at a specified severity level where severitylevel means the conditions used -- that is, the temperature, pressure,contact time and presence of diluents such as H₂ ; (2) selectivityrefers to the amount of desired product or products obtained relative tothe amount of reactants charged or converted; (3) stability refers tothe rate of change with time of the activity and selectivity parameters-- obviously, the smaller rate implying the more stable catalyst. In areforming process, for example, activity commonly refers to the amountof conversion that takes place for a given charge stock at a specifiedseverity level and is typically measured by octane number of the C₅ +product stream; selectivity refers to the amount of C₅ + yield, relativeto the amount of the charge, that is obtained at the particular activityor severity level; and stability is typically equated to the rate ofchange with time of activity, as measured by octane number of C₅ +product, and of selectivity as measured by C₅ + yield. Actually, thelast statement is not strictly correct because generally a continuousreforming process is run to produce a constant octane C₅ + product withseverity level being continuously adjusted to attain this result; andfurthermore, the severity level is for this process usually varied byadjusting the conversion temperature in the reaction zone so that, inpoint of fact, the rate of change of activity finds response in the rateof change of conversion temperatures and changes in this last parameterare customarily taken as indicative of activity stability.

As is well known to those skilled in the art, the principal cause ofobserved deactivation or instability of a dual-function catalyst when itis used in a hydrocarbon conversion reaction is associated with the factthat coke forms on th surface of the catalyst during the course of thereaction. More specifically, in these hydrocarbon conversion processes,the conditions utilized typically result in the formation of heavy, highmolecular weight, black, solid or semi-solid, carbonaceous materialwhich is a hydrogen-deficient polymeric substance having properties akinto both polynuclear aromatics and graphite. This material coats thesurface of the catalyst and thus reduces its activity by shielding itsactive sites from the reactants. In other words, the performance of thisdual-function catalyst is sensitive to the presence of carbonaceousdeposits or coke on the surface of the catalyst. Accordingly, the majorproblem facing workers in this area of the art is the development ofmore active and/or selective catalytic composites that are not assensitive to the presence of these carbonaceous materials and/or havethe capability to suppress the rate of the formation of thesecarbonaceous materials on the catalyst. Viewed in terms of performanceparameters, the problem is to develop a dual-function catalyst havingsuperior activity, selectivity and stability characteristics. Inparticular, for a reforming process the problem is typically expressedin terms of shifting and stabilizing the C₅ + yield-octane relationshipat the lowest possible severity level -- C₅ + yield being representativeof selectivity and octane being proportional to activity.

We have now found a dual-function acidic multimetallic catalyticcomposite which possesses improved activity, selectivity, and stabilitycharacteristics when it is employed in a process for the conversion ofhydrocarbons of the type which have heretofore utilized dual-functionacidic catalytic composites such as processes for isomerization,hydroisomerization, dehydrogenation, desulfurization, denitrogenization,hydrogenation, alkylation, dealkylation, disproportionation,polymerization, hydrodealkylation, transalkylation, cyclization,dehydrocyclization, cracking, hydrocracking, halogenation, reforming andthe like processes. In particular, we have ascertained that an acidiccatalyst, comprising a combination of catalytically effective amounts ofa platinum group component, a rhenium component, a cobalt component, atin component and a halogen component with a porous refractory carriermaterial, can enable the performance of hydrocarbon conversion processesutilizing dual-function catalysts to be substantially improved if themetallic components are uniformly dispersed throughout the carriermaterial and if their oxidation states are controlled to be in thestates hereinafter specified. Moreover, we have determined that anacidic catalytic composite, comprising a combination of catalyticallyeffective amounts of a platinum group component, a rhenium component, atin component, a cobalt component, and a chloride component with analumina carrier material, can be utilized to substantially improve theperformance of a reforming process which operates on a low-octanegasoline fraction to produce a high-octane reformate if the metalliccomponents are uniformly dispersed throughout the alumina carriermaterial, if the average crystallite or particle size of the tin andcobalt components are less than 100 Angstroms in maximum dimension andif the oxidation states of the metallic components are fixed in thestate hereinafter specified. In the case of a reforming process, theprincipal advantage associated with the use of the present inventioninvolves the acquisition of the capability to operate in a stable mannerin a high severity operation; for example, a low or moderate pressurereforming process designed to produce a C₅ + reformate having an octaneof about 100 F-1 clear. As indicated, the present invention essentiallyinvolves the finding that the addition of a combination of a rheniumcomponent, a tin component and a cobalt component to a dual-functionacidic hydrocarbon conversion catalyst containing a platinum groupcomponent can enable the performance characteristics of the catalyst tobe sharply and materially improved, if the hereinafter specifiedlimitations on amounts of ingredients, particle size of tin and cobaltmoieties, oxidation states of metals, and distribution of metalliccomponents in the support are met.

It is, accordingly, one object of the present invention to provide anacidic multimetallic hydrocarbon conversion catalyst having superiorperformance characteristics when utilized in a hydrocarbon conversionprocess. A second object is to provide an acidic multimetallic catalysthaving dual-function hydrocarbon conversion performance characteristicsthat are relatively insensitive to the deposition of hydrocarbonaceousmaterial thereon. A third object is to provide preferred methods ofpreparation of this acidic multimetallic catalytic composite whichinsures the achievement and maintenance of its properties. Anotherobject is to provide an improved reforming catalyst having superioractivity, selectivity, and stability characteristics. Yet another objectis to provide a dual-function hydrocarbon conversion catalyst whichutilizes a combination of a rhenium component, a tin component and acobalt component to beneficially interact with and promote an acidiccatalyst containing a platinum group component.

In brief summary, the present invention is, in one embodiment, an acidiccatalyst composite comprising a porous carrier material containing, onan elemental basis, about 0.01 to about 2 wt. % platinum group metal,about 0.01 to about 2 wt. % rhenium, about 0.05 to about 5 wt. % cobalt,about 0.01 to about 5 wt. % tin, and about 0.1 to about 3.5 wt. %halogen, wherein the platinum group metal, rhenium, tin and cobalt areuniformly dispersed throughout the porous carrier material, whereinsubstantially all of the platinum group metal is present in theelemental metallic state, wherein substantially all of the tin ispresent in an oxidation state above that of the elemental metal andwherein substantially all of the cobalt and rhenium are present in thecorresponding elemental metallic state or in a state which is reducibleto the corresponding elemental metallic state under hydrocarbonconversion conditions or in a mixture of these states.

A second embodiment relates to a catalytic composite comprising a porouscarrier material containing, on an elemental basis, about 0.05 to about1 wt. % platinum group metal, about 0.05 to about 1 wt. % rhenium, about0.10 to about 2.5 wt. % cobalt, about 0.05 to about 1 wt. % tin, andabout 0.5 to about 1.5 wt. % halogen, wherein the platinum group metal,rhenium, tin and cobalt are uniformly dispersed throughout the porouscarrier material, wherein substantially all of the platinum group metalis present in the corresponding elemental metallic state, whereinsubstantially all of the tin is present in an oxidation state above thatof the elemental metal and wherein substantially all of the cobalt andrhenium are present in the corresponding elemental metallic state or ina state which is reducible to the corresponding elemental metallic stateunder hydrocarbon conversion conditions or in a mixture of these states.

A third embodiment relates to the catalytic composite described in thefirst or second embodiment wherein the halogen is combined chloride.

Yet another embodiment involves a process for the conversion of ahydrocarbon comprising contacting the hydrocarbon and hydrogen with thecatalytic composite described above in the first or second or thirdembodiment at hydrocarbon conversion conditions.

A preferred embodiment comprehends a process for reforming a gasolinefraction which comprises contacting the gasoline fraction and hydrogenwith the catalytic composite described above in the first or second orthird embodiment at reforming conditions selected to produce a highoctane reformate.

A highly preferred embodiment is a process for reforming a gasolinefraction which comprises contacting the gasoline fraction and hydrogenin a substantially water-free and sulfur-free environment with thecatalytic composite characterized in the first, second or thirdembodiment at reforming conditions selected to produce a high octanereformate.

Other objects and embodiments of the present invention relate toadditional details regarding preferred catalytic ingredients, preferredamounts of ingredients, suitable methods of composite preparation,operating conditions for use in the hydrocarbon conversion processes,and the like particulars, which are hereinafter given in the followingdetailed discussion of each of these facets of the present invention.

The acidic multimetallic catalyst of the present invention comprises aporous carrier material or support having combined therewithcatalytically effective amounts of a platinum group component, a rheniumcomponent, a cobalt component, a tin component and a halogen component.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high-surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the hydrocarbon conversion process, and it isintended to include within the scope of the present invention carriermaterials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts such as: (1) activated carbon, coke orcharcoal; (2) silica or silica gel, silicon carbide, clays and silicatesincluding those synthetically prepared and naturally occurring, whichmay or may not be acid treated, for example, attapulgus clay, chinaclay, diatomaceous earth, fuller's earth, kaolin, keiselguhr, etc., (3)ceramics, porcelain, crushed firebrick, bauxite; (4) refractoryinorganic oxides such as alumina, titanium dioxide, zirconium dioxide,chromium oxide, beryllium oxide, vanadium oxide, cesium oxide, hafniumoxide, zinc oxide, magnesia, boria, thoria, silica-alumina,silica-magnesia, chromia-alumina, alumina-boria, silica-zirconia, etc.;(5) crystalline zeolitic aluminosilicates such as naturally occurring orsynthetically prepared mordenite and/or faujasite, either in thehydrogen form or in a form which has been treated with multivalentcations; (6) spinels such as MgAl₂ O₄, FeAl₂ O₄, ZnAl₂ O₄, MnAl₂ O₄,CaAl₂ O₄ and other like compounds having the formula MO.sup.. Al₂ O₃where M is a metal having a valence of 2; and (7) combinations ofelements from one or more of these groups. The preferred porous carriermaterials for use in the present invention are refractory inorganicoxides, with best results obtained with an alumina carrier material.Suitable alumina materials are the crystalline aluminas known as gamma-,eta- and theta-alumina, with gamma- or eta-alumina giving best results.In addition, in some embodiments the alumina carrier material maycontain minor proportions of other well-known refractory inorganicoxides such as silica, zirconia, magnesia, etc.; however, the preferredsupport is substantially pur gamma- or eta-alumina. Preferred carriermaterials have an apparent bulk density of about 0.3 to about 0.8 g/ccand surface area characteristics such that the average pore diameter isabout 20 to 300 Angstroms, the pore volume is about 0.1 to about 1 cc/gand the surface area is about 100 to about 500 m² /g. In general, bestresults are typically obtained with a gamma-alumina carrier materialwhich is used in the form of spherical particles having: a relativelysmall diameter (i.e. typically about 1/16 inch), an apparent bulkdensity of about 0.3 to about 0.8 g/cc, a pore volume of about 0.4 ml/gand a surface area of about 200 m² /g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide, to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, tablets, etc., and utilized in anydesired size. For the purpose of the present invention, a particularlypreferred form of alumina is the sphere; and alumina spheres may becontinuously manufactured by the well-known oil drop method whichcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid, combining the resultant hydrosol with a suitable gelling agent anddropping the resultant mixture into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen washed and dried at a relatively low temperature of about 300° F.to about 400° F. and subjected to a calcination procedure at atemperature of about 850° F. to about 1300° F. for a period of about 1to about 20 hours. This treatment effects conversion of the aluminahydrogel to the corresponding crystalline gamma-alumina. See theteachings of U.S. Pat. No. 2,620,314 for additional details.

One essential constituent of the acidic multimetallic composite used inthe present invention is a tin component, and it is an essential featureof the present invention that substantially all of the tin component inthe composite is in an oxidation state above that of the elementalmetal. That is, it is believed that best results are obtained whensubstantially all of the tin component exists in the catalytic compositein the +2 or +4 oxidation state. Accordingly, the tin component will bepresent in the composite as a chemical compound such as the oxide,halide, oxyhalide, and the like, wherein the tin moiety is in a positiveoxidation state, or in chemical combination with the carrier material ina manner such that the tin component is in a positive oxidation state.Controlled reduction experiments with tin-containing catalyticcomposites produced by the preferred methods of preparing the instantcatalytic composite have established that the tin component in thesecatalysts is in a positive oxidation state and is not reduced by contactwith hydrogen at temperatures in the range of 1000° to 1200° F. It isimportant to note that this limitation on the oxidation state of the tincomponent requires extreme care in preparation and use of the presentcatalyst to insure that it is not subjected to a reducing atmosphere attemperatures above 1200° F. Equally significant is the observation thatit is only when the tin component is in a uniformly dispersed state inthe carrier material that it has the capability to maintain its positiveoxidation state when subjected to hereinafter described prereductionstep. Stated another way, if the tin component is not properly dispersedon the support, it can be reduced in the prereduction step and result inan inferior catalyst. Based on the evidence currently available, it isbelieved that best results are obtained when the tin component ispresent in the catalyst as tin oxide. The term "tin oxide" as usedherein refers to a coordinated tin-oxygen complex which is notnecessarily stoichiometric.

Interrelated with this oxidation state limitation are the factors ofdispersion of the tin component in the support and of particle size ofthe tin component. It has been established that it is only when the tincomponent is uniformly dispersed throughout the carrier material in aparticle or crystallite size having a maximum dimension less than 100Angstroms that it can successfully maintain its preferred oxidationstate when it is subjected to a high temperature prereduction treatmentor to hydrocarbon conversion conditions hereinafter described. Thus itis an essential feature of our invention that the instant acidicmultimetallic catalytic composite is prepared in a manner selected tomeet the stated particle size and uniform dispersion limitations. By theuse of the expression "uniform dispersion of a specified component inthe carrier material" it is intended to describe the situation where theconcentration of the specified ingredient is approximately the same inany reasonably divisable portion of the carrier material. Similarly, theexpression "particles or crystallites having a maximum dimension lessthan 100° A" is intended to denote particles that would pass through asieve having a 100° A mesh size if it were possible to make such asieve.

The tin component may be incorporated into the catalytic composite inany suitable manner known to effectively disperse this componentthroughout the carrier material in the required particle size. Thus thiscomponent may be added to the carrier by coprecipitation or cogellationof a suitable soluble tin salt with the carrier material, byion-exchange of suitable tin ions with ions contained in the carriermaterial when the ion-exchange sites are uniformly distributedthroughout the carrier or controlled impregnation of the carriermaterial with a suitable soluble tin salt under conditions selected toresult in penetration of all sections of the carrier material by the tincomponent. One preferred method of incorporating the tin componentinvolves coprecipitating or cogelling it during the preparation of thepreferred carrier material, alumina. This method typically involves theaddition of a suitable soluble tin compound such as stannous or stannicchloride to an alumina hydrosol, mixing these ingredients to obtain auniform distribution of the tin moiety throughout the sol and thencombining the hydrosol with a suitable gelling agent and dropping theresulting mixture into an oil bath, etc., as explained in detailhereinbefore. After drying and calcining the resulting gelled carriermaterial, there is obtained an intimate combination of alumina and tinoxide having the required dispersion and particle size. Anotherpreferred method of incorporating the tin component into the catalyticcomposite involves utilization of a soluble, decomposable compound oftin to impregnate the porous carrier material. In general, the solventused in this impregnation step is selected on the basis of thecapability to dissolve the desired tin compound and to hold the tinmoiety in solution until it is evenly distributed throughout the carriermaterial and is preferably an aqueous, rather strongly acidic solution.Thus the tin component may be added to the carrier material bycommingling the latter with an aqueous solution of a suitable tin saltor suitable compound of tin such as stannous bromide, stannous chloride,stannic chloride, stannic chloride pentahydrate, stannic chloridediamine, stannic trichloride bromide, stannic chromate, stannousfluoride, stannic fluoride, stannic iodide, stannic sulfate, stannictartrate and the like compounds. The acid used in the impregnationsolution may be any organic or inorganic acid that is capable ofmaintaining the pH of the impregnation solution in the range of about -1or less to about 3 and preferably less than 1 during the impregnationstep and that does not contaminate the resultant catalyst. Suitableacids are: inorganic acids such as hydrochloric acid, nitric acid andthe like; and strongly acidic organic acids such as oxalic acid, malonicacid, citric acid, malic acid, formic acid, tartaric acid, and the like.A particularly preferred impregnation solution comprises stannic orstannous chloride dissolved in a hydrochloric acid solution containingHCl in an amount corresponding to at least about 5 wt. % of the carriermaterial which is to be impregnated. Another useful impregnationsolution is stannous or stannic chloride dissolved in an anhydrousalcohol such as ethanol. In general, the tin component can beincorporated either prior to, simultaneously with, or after the othermetallic components are added to the carrier material. However, we havefound that excellent results are obtained when the tin component isincorporated in the carrier material during its preparation and theother metallic components are added in a subsequent impregnation stepafter the tin-containing carrier material is calcined.

Regarding the amount of the tin component contained in the instantcomposite, it is preferably sufficient to constitute about 0.01 to about5 wt. % of the final composite, calculated on an elemental basis,although substantially higher amounts of tin may be utilized in somecases. Best results are typically obtained with about 0.1 to about 1 wt.% tin.

A second essential ingredient of the subject catalyst is the platinumgroup component. That is, it is intended to cover the use of platinum,iridium, osmium, ruthenium, rhodium, palladium or mixtures thereof as asecond component of the present composite. It is an essential feature ofthe present invention that substantially all of this platinum groupcomponent exists within the final catalytic composite in the elementalmetallic state. Generally, the amount of this component present in thefinal catalytic composite is small compared to the quantities of theother components combined therewith. In fact, the platinum groupcomponent generally will comprise about 0.01 to about 2 wt. % of thefinal catalytic composite, calculated on an elemental basis. Excellentresults are obtained when the catalyst contains about 0.05 to about 1wt. % of platinum, iridium, rhodium or palladium metal. Particularlypreferred mixtures of these metals are platinum and iridium and platinumand rhodium.

This platinum group component may be incorporated in the catalyticcomposite in any suitable manner known to result in a relatively uniformdistribution of this component in the carrier material such ascoprecipitation or cogellation, ion exchange or impregnation. Thepreferred method of preparing the catalyst involves the utilization of asoluble, decomposable compound of platinum group metal to impregnate thecarrier material in a relatively uniform manner. For example, thiscomponent may be added to the support by commingling the latter with anaqueous solution of chloroplatinic or chloroiridic or chloropalladicacid. Other water-soluble compounds or complexes of platinum groupmetals may be employed in impregnation solutions and include ammoniumchloroplatinate, bromoplatinic acid, platinum trichloride, platinumtetrachloride hydrate, platinum dichlorocarbonyl dichloride,dinitrodiaminoplatinum, sodium tetranitroplatinate (II), palladiumchloride, palladium nitrate, palladium sulfate, diamminepalladium (II)hydroxide, tetramminepalladium (II) chloride, hexamminerhodium chloride,rhodium carbonylchloride, rhodium trichloride hydrate, rhodium nitrate,sodium hexachlororhodate (III), sodium hexanitrorhodate (III), iridiumtribromide, iridium dichloride, iridium tetrachloride, sodiumhexanitroiridate (III), potassium or sodium chloroiridate, potassiumrhodium oxalate, etc. The utilization of a platinum, iridium, rhodium orpalladium chloride compound, such as chloroplatinic, chloroiridic orchloropalladic acid or rhodium trichloride hydrate, is preferred sinceit facilitates the incorporation of both the platinum group componentsand at least a minor quantity of the halogen component in a single step.Hydrogen chloride or the like acid is also generally added to theimpregnation solution in order to further facilitate the incorporationof the halogen component and the uniform distribution of the metalliccomponents through the carrier material. In addition, it is generallypreferred to impregnate the carrier material after it has been calcinedin order to minimize the risk of washing away the valuable platinum orpalladium compounds; however, in some cases it may be advantageous toimpregnate the carrier material when it is in a gelled state.

Another essential ingredient of the present catalytic composite is arhenium component. It is of fundamental importance that substantiallyall of the rhenium component exists within the catalytic composite ofthe present invention in the elemental metallic state or in a statewhich is reducible to the elemental state under hydrocarbon conversionconditions or in a mixture of these states. The rhenium component may beutilized in the composite in any amount which is catalyticallyeffective, with the preferred amount being about 0.01 to about 2 wt. %thereof, calculated on an elemental basis. Typically, best results areobtained with about 0.05 to about 1 wt. % rhenium. It is additionallypreferred to select the specified amount of rhenium from within thisbroad weight range as a function of the amount of the platinum groupcomponent, on an atomic basis, as is explained hereinafter.

This rhenium component may be incorporated into the catalytic compositein any suitable manner known to those skilled in the catalystformulation art which results in a relatively uniform distribution ofrhenium in the carrier material such as by coprecipitation,ion-exchange, or impregnation. In addition, it may be added at any stageof the preparation of the composite -- either during preparation of thecarrier material or thereafter -- and the precise method ofincorporation used is not deemed to be critical. However, best resultsare obtained when the rhenium component is relatively uniformlydistributed throughout the carrier material in a relatively smallparticle size, and the preferred procedures are the ones known to resultin a composite having this relatively uniform distribution. Oneacceptable procedure for incorporating this component into the compositeinvolves cogelling or coprecipitating the rhenium component during thepreparation of the preferred carrier material, alumina. This procedureusually comprehends the addition of a soluble, decomposable compound ofrhenium such as perrhenic acid or a salt thereof to the alumina hydrosolbefore it is gelled. The resulting mixture is then finished byconventional gelling, aging, drying, and calcination steps as explainedhereinbefore. A preferred way of incorporating this component is animpregnation step wherein the porous carrier material is impregnatedwith a suitable rhenium-containing solution either before, during, orafter the carrier material is calcined. Preferred impregnation solutionsare aqueous solutions of water soluble, decomposable rhenium compoundssuch as ammonium perrhenates, sodium perrhenate, potassium perrhenate,potassium rhenium oxychloride (K₂ ReOCl₅), potassium hexachlororhenate(IV), rhenium chloride, rhenium heptoxide, and the like compounds. Bestresults are ordinarily obtained when the impregnation solution is anaqueous solution of perrhenic acid. This component can be added to thecarrier material either prior to, simultaneously with, or after theother metallic components are combined therewith. Best results areusually achieved when this component is added simultaneously with theplatinum group and cobalt components. In fact, excellent results areobtained as shown in the Examples with a one-step impregnation procedureusing a tin-containing carrier material and an acidic aqueousimpregnation solution containing chloroplatinic acid, perrhenic acid,cobaltous chloride, and hydrochloric acid.

Yet another essential ingredient of the acidic multimetallic catalyticcomposite of the present invention is a cobalt component. Although thiscomponent may be initially incorporated into the composite in manydifferent decomposable forms which are hereinafter stated, our basicfinding is that the catalytically active state for hydrocarbonconversion with this component is the elemental metallic state.Consequently, it is a feature of our invention that substantially all ofthe cobalt component exists in the catalytic composite either in theelemental metallic state or in a state which is reducible to theelemental state under hydrocarbon conversion conditions or in a mixtureof these states. Examples of this last state are obtained when thecobalt component is initially present in the form of cobalt oxide,hydroxide, halide, oxyhalide and the like reducible compounds. As acorollary to this basic finding on the active state of the cobaltcomponent, it follows that the presence of cobalt in forms which are notreducible at hydrocarbon conversion conditions is to be scrupulouslyavoided if the full benefits of the present invention are to berealized. Illustrative of these undesired forms are cobalt sulfide andthe cobalt oxysulfur compounds such as cobalt sulfate. Best results areobtained when the composite initially contains all of the cobaltcomponent in the elemental metallic state or in a reducible oxide stateor in a mixture of these states. All available evidence indicates thatthe preferred preparation procedure specifically described in Example Iresults in a catalyst having the cobalt component in a reducible oxideform. The cobalt component may be utilized in the composite in anyamount which is catalytically effective, with the preferred amount beingabout 0.05 to about 5 wt. % thereof, calculated on an elemental cobaltbasis. Typically, best results are obtained with about 0.10 to about 2.5wt % cobalt. It is, additionally, preferred to select the specificamount of cobalt from within this broad weight range as a function ofthe amount of the platinum group component, on an atomic basis, as isexplained hereinafter.

The cobalt component may be incorporated into the catalytic composite inany suitable manner known to those skilled in the catalyst formulationart to result in a relatively uniform distribution of cobalt in thecarrier material such as coprecipitation, cogellation, ion exchange,impregnation, etc. In addition, it may be added at any stage of thepreparation of the composite -- either during preparation of the carriermaterial or thereafter -- since the precise method of incorporation usedis not deemed to be critical. However, best results are obtained whenthe cobalt component is relatively uniformly distributed throughout thecarrier material in a relatively small particle or crystallite sizehaving a maximum dimension of less than 100 Angstroms, and the preferredprocedures are the ones that are known to result in a composite having arelatively uniform distribution of the cobalt moiety in a relativelysmall particle size. One acceptable procedure for incorporating thiscomponent into the composite involves cogelling or coprecipitating thecobalt component during the preparation of the preferred carriermaterial, alumina. This procedure usually comprehends the addition of asoluble, decomposable, and reducible compound of cobalt such as cobaltchloride or nitrate to the alumina hydrosol before it is gelled.Alternatively, the compound of cobalt can be added to the gelling agent.The resulting mixture is then finished by conventional gelling, aging,drying and calcination steps as explained hereinbefore. One preferredway of incorporating this component is an impregnation step wherein theporous carrier material is impregnated with a suitable cobalt-containingsolution either before, during or after the carrier material is calcinedor oxidized. The solvent used to form the impregnation solution may bewater, alcohol, ether or any other suitable organic or inorganic solventprovided the solvent does not adversely interact with any of the otheringredients of the composite or interfere with the distribution andreduction of the cobalt component. Preferred impregnation solutions areaqueous solutions of water-soluble, decomposable, and reducible cobaltcompounds such as cobaltous acetate, cobaltous benzoate, cobaltousbromate, cobaltous bromide, cobaltous chlorate and perchlorate,cobaltous chloride, cobaltic chloride, cobaltous fluoride, cobaltousiodide, cobaltous nitrate, hexamminecobalt (III) chloride,hexamminecobalt (III) nitrate, triethylenediamminecobalt (III) chloride,cobaltous hexamethylenetetramine, and the like compounds. Best resultsare ordinarily obtained when the impregnation solution is an aqueoussolution of cobalt chloride or cobalt nitrate. This cobalt component canbe added to the carrier material, either prior to, simultaneously with,or after the other metallic components are combined therewith. Bestresults are usually achieved when this component is added simultaneouslywith the platinum group and rhenium components via an acidic aqueousimpregnation solution. In fact, excellent results are obtained, asreported in the examples, with an impregnation precedure using atin-containing carrier material and an acidic aqueous solutioncomprising chloroplatinic acid, perrhenic acid, cobaltous chloride andhydrochloric acid.

It is essential to incorporate a halogen component into the acidicmultimetallic catalytic composite of the present invention. Although theprecise form of the chemistry of the association of the halogencomponent with the carrier material is not entirely known, it iscustomary in the art to refer to the halogen component as being combinedwith the carrier material, or with the other ingredients of the catalystin the form of the halide (e.g. as the chloride). This combined halogenmay be either fluorine, chlorine, iodine, bromine or mixtures thereof.Of these, fluorine and particularly chlorine are preferred for thepurposes of the present invention. The halogen may be added to thecarrier material in any suitable manner, either during preparation ofthe support or before or after the addition of the other components. Forexample, the halogen may be added, at any stage of the preparation ofthe carrier material or to the calcined carrier material, as an aqueoussolution of a suitable, decomposable halogencontaining compound such ashydrogen fluoride, hydrogen chloride, hydrogen bromide, ammoniumchloride, etc. The halogen component or a portion thereof, may becombined with the carrier material during the impregnation of the latterwith the platinum group, rhenium, cobalt or tin components; for example,through the utilization of a mixture of chloroplatinic acid and hydrogenchloride. In another situation, the alumina hydrosol which is typicallyutilized to form the preferred alumina carrier material may containhalogen and thus contribute at least a portion of the halogen componentto the final composite. For reforming, the halogen will be typicallycombined with the carrier material in an amount sufficient to result ina final composite that contains about 0.1 to about 3.5% and preferablyabout 0.5 to about 1.5% by weight halogen, calculated on an elementalbasis. In isomerization or hydrocracking embodiments, it is generallypreferred to utilize relatively larger amounts of halogen in thecatalyst -- typically ranging up to about 10 wt. % halogen calculated onan elemental basis, and more preferably, about 1 to about 5 wt. %. It isto be understood that the specified level of halogen component in theinstant catalyst can be achieved or maintained during use in theconversion of hydrocarbons by continuously or periodically adding to thereaction zone a decomposable halogen-containing compound such as anorganic chloride (e.g. ethylene dichloride, carbon tetrachloride,t-butyl chloride) in an amount of about 1 to 100 wt. ppm of thehydrocarbon feed, and preferably about 1 to 10 wt. ppm.

Regarding especially preferred amounts of the various metalliccomponents of the subject catalyst, we have found it to be a goodpractice to specify the amounts of the cobalt, rhenium and tincomponents as a function of the amount of the platinum group component.On this basis, the amount of the cobalt component is ordinarily selectedso that the atomic ratio of cobalt to platinum group metal contained inthe composite is about 0.1:1 to about 66:1, with the preferred rangebeing about 0.4:1 to about 18:1. Similarly, the amount of the tincomponent is ordinarily selected to produce a composite containing anatomic ratio of tin to platinum or palladium metal of about 0.1:1 toabout 13:1, with the preferred range being about 0.3:1 to about 5:1. Theamount of the rhenium component is likewise set to correspond to anatomic ratio of rhenium to platinum group metal of about 0.05:1 to 10:1,with a ratio of 0.2:1 to 5:1 being preferred.

Another significant parameter for the instant catalyst is the "totalmetals content" which is defined to be the sum of the platinum groupcomponent, the rhenium component, the cobalt component, and the tincomponent, calculated on an elemental basis. Good results are ordinarilyobtained with the subject catalyst when this parameter is fixed at avalue of about 0.15 to about 4 wt. %, with best results ordinarilyachieved at a metals loading of about 0.3 to about 3 wt. %.

In embodiments of the present invention wherein the instantmultimetallic catalytic composite is used for the dehydrogenation ofdehydrogenatable hydrocarbons or for the hydrogenation of hydrogenatablehydrocarbons, it is ordinarily a preferred practice to include an alkalior alkaline earth metal component in the composite and to minimize oreliminate the halogen component. More precisely, this optionalingredient is selected from the group consisting of the compounds of thealkali metals -- cesium, rubidium, potassium, sodium, and lithium -- andthe compounds of the alkaline earth metals -- calcium, strontium, bariumand magnesium. Generally, good results are obtained in these embodimentswhen this component constitutes about 0.1 to about 5 wt. % of thecomposite, calculated on an elemental basis. This optional alkali oralkaline earth metal component can be incorporated in the composite inany of the known ways, with impregnation with an aqueous solution of asuitable water-soluble, decomposable compound being preferred.

An optional ingredient for the multimetallic catalyst of the presentinvention is a Friedel-Crafts metal halide component. This ingredient isparticularly useful in hydrocarbon conversion embodiments of the presentinvention wherein it is preferred that the catalyst utilized has astrong acid or cracking function associated therewith -- for example, anembodiment wherein hydrocarbons are to be hydrocracked or isomerizedwith the catalyst of the present invention. Suitable metal halides ofthe Friedel-Crafts type include aluminum chloride, aluminum bromide,ferric chloride, ferric bromide, zinc chloride and the like compounds,with the aluminum halides and particularly aluminum chloride ordinarilyyielding best results. Generally, this optional ingredient can beincorporated into the composite of the present invention by any of theconventional methods for adding metallic halides of this type; however,best results are ordinarily obtained when the metallic halide issublimed onto the surface of the carrier material according to thepreferred method disclosed in U.S. Pat. No. 2,999,074. The component cangenerally be utilized in any amount which is catalytically effective,with a value selected from the range of about 1 to about 100 wt. % ofthe carrier material generally being preferred.

Regardless of the details of how the components of the catalyst arecombined with the porous carrier material, the final catalyst generallywill be dried at a temperature of about 200° to about 600° F. for aperiod of at least about 2 to about 24 hours or more, and finallycalcined or oxidized at a temperature of about 700° F. to about 1100° F.in an air or oxygen atmosphere for a period of about 0.5 to about 10hours in order to convert substantially all of the metallic componentsto the corresponding oxide form. Because a halogen component is utilizedin the catalyst, best results are generally obtained when the halogencontent of the catalyst is adjusted during the oxidation step byincluding a halogen or a halogencontaining compound such as HCl in theair or oxygen atmosphere utilized. In particular, when the halogencomponent of the catalyst is chlorine, it is preferred to use a moleratio of H₂ O to HCl of about 5:1 to about 100:1 during at least aportion of the oxidation step in order to adjust the final chlorinecontent of the catalyst to a range of about 0.1 to about 3.5 wt. %.Preferably, the duration of this halogenation step is about 1 to 5hours.

The resultant oxidized catalytic composite is preferably subjected to asubstantially water-free and hydrocarbon-free reduction step prior toits use in the conversion of hydrocarbons. This step is designed toselectively reduce at least the platinum group component to theelemental metallic state and to insure a uniform and finely divideddispersion of the metallic components throughout the carrier material,while maintaining the tin component in a positive oxidation state.Preferably substantially pure and dry hydrogen (i.e. less than 20 vol.ppm, H₂ O) is used as the reducing agent in this step. The reducingagent is contacted with the oxidized catalyst at conditions including areduction temperature of about 800° F. to about 1200° F. and a period oftime of about 0.5 to 10 hours effective to reduce substantially all ofthe platinum group component to the elemental metallic state whilemaintaining the tin component in an oxidation state above that of theelemental metal. Quite surprisingly, we have found that if thisreduction step is performed with a hydrocarbon-free hydrogen stream atthe temperature indicated and if the cobalt component is properlydistributed in the carrier material in the oxide form and in thespecified particle size, no substantial amount of the cobalt componentwill be reduced in this step. However, once the catalyst sees a mixtureof hydrogen and hydrocarbon (such as during the starting-up andlining-out of the hydrocarbon conversion process using same),substantially all of the cobalt component is quickly reduced at thespecified reduction temperature range. This reduction treatment may beperformed in situ as part of a start-up sequence if precautions aretaken to predry the plant to a substantially water-free state and ifsubstantially water-free and hydrocarbon-free hydrogen is used.Unambiguous evidence on the oxidation state of the rhenium componentafter this reduction step is not presently available; however, we havefound that after the instant catalyst is started-up and lined-out athydrocarbon conversion conditions substantially all of the rheniumcomponent is present as elemental metallic rhenium.

The resulting reduced catalytic composite is, in accordance with thebasic concept of the present invention, preferably maintained in asulfur-free state both during its preparation and thereafter during itsuse in the conversion of hydrocarbons. As indicated previously, thebeneficial interaction of the cobalt component with the otheringredients of the present catalytic composite is contingent upon themaintenance of the cobalt moiety in a highly dispersed, readilyreducible state in the carrier material. Sulfur in the form of sulfideadversely interfers with both the dispersion and reducibility of tecobalt component and consequently it is a highly preferred practice toavoid presulfiding the reduced acidic multimetallic catalyst resultingfrom the reduction step. Once the catalyst has been exposed tohydrocarbon for a sufficient period of time to lay down a protectivelayer of carbon or coke on the surface thereof, the sulfur sensitivityof the resulting carbon-containing composite changes rather markedly andthe presence of small amounts of sulfur can be tolerated withoughpermanently disabling the catalyst. The exposure of the freshly reducedcatalyst to sulfur can seriously damage the cobalt component thereof andconsequently jeopardize the superior performance characteristicsassociated therewith. However, once a protective layer of carbon isestablished on the catalyst, the sulfur deactivation effect is lesspermanent and sulfur can be purged therefrom by exposure to asulfur-free hydrogen stream at a temperature of about 800° to 1100°F.

According to the present invention, a hydrocarbon charge stock andhydrogen are contacted with the instant acidic multimetallic catalyst ina hydrocarbon conversion zone. This contacting may be accomplished byusing the catalyst in a fixed bed system, a moving bed system, afluidized bed system, or in a batch type operation; however, in view ofthe danger of attrition losses of the valuable catalyst and ofwell-known operational advantages, it is preferred to use either a fixedbed system or a densephase moving bed system such as is shown in U.S.Pat. No. 3,725,249. It is also contemplated that the contacting step canbe performed in the presence of a physical mixture of particles of thecatalyst of the present invention and particles of a conventionaldual-function catalyst of the prior art. In a fixed bed system, ahydrogen-rich gas and the charge stock are preheated by any suitableheating means to the desired reaction temperature and then are passedinto a conversion zone containing a fixed bed of the acidicmultimetallic catalyst. It is, of course, understood that the conversionzone may be one or more separate reactors with suitable meanstherebetween to insure that the desired conversion temperature ismaintained at the entrance to each reactor. It is also important to notethat the reactants may be contacted with the catalyst bed in eitherupward, downward or radial flow fashion with the latter being preferred.In addition, the reactants may be in the liquid phase, a mixedliquid-vapor phase, or a vapor phase when they contact the catalyst,with best results obtained in the vapor phase.

In the case where the acidic multimetallic catalyst of the presentinvention is used in a reforming operation, the reforming system willtypically comprise a reforming zone containing one or more fixed beds ordense-phase moving beds of the catalyst. In a multiple bed system, it isof course within the scope of the present invention to use the presentcatalyst in less than all of the beds with a conventional dual-functioncatalyst being used in the remainder of the beds. This reforming zonemay be one or more separate reactors with suitable heating meanstherebetween to compensate for the endothermic nature of the reactionsthat take place in each catalyst bed. The hydrocarbon feed stream thatis charged to this reforming system will comprise hydrocarbon fractionscontaining naphthenes and paraffins that boil within the gasoline range.The preferred charge stocks are those consisting essentially ofnaphthenes and paraffins, although in some cases aromatics and/orolefins may also be present. This preferred class includes straight rungasolines, natural gasolines, synthetic gasolines, partially reformedgasolines, and the like. On the other hand, it is frequentlyadvantageous to charge thermally or catalytically cracked gasoline orhigher boiling fractions thereof. Mixtures of straight run and crackedgasolines can also be used to advantage. The gasoline charge stock maybe a full boiling gasoline having an initial boiling point of from about50° to about 150°F. and an end boiling point within the range of fromabout 325° to about 425°F., or may be a selected fraction thereof whichgenerally will be a higher boiling fraction commonly referred to as aheavy naphtha -- for example, a naphtha boiling in the range of C₇ to400°F. In some cases, it is also advantageous to charge purehydrocarbons or mixtures of hydrocarbons that have been extracted fromhydrocarbon distillates -- for example, straight-chain paraffins --which are to be converted to aromatics. It is preferred that thesecharge stocks be treated by conventional catalytic pretreatment methodssuch as hydrorefining, hydrotreating, hydrodesulfurization, etc., toremove substantially all sulfurous, nitrogenous and water-yieldingcontaminants therefrom and to saturate any olefins that may be containedtherein.

In other hydrocarbon conversion embodiments, the charge stock will be ofthe conventional type customarily used for the particular kind ofhydrocarbon conversion being effected. For example, in a typicalisomerization embodiment the charge stock can be a paraffinic stock richin C₄ to C₈ normal paraffins, or a normal butane-rich stock, or annhexane-rich stock, or a mixture of xylene isomers, etc. In adehydrogenation embodiment, the charge stock can be any of the knowndehydrogenatable hydrocarbons such as an aliphatic compound containing 2to 30 carbon atoms per molecule, a C₄ to C₃₀ normal paraffin, a C₈ toC₁₂ alkylaromatic, a naphthene and the like. In hydrocrackingembodiments, the charge stock will be typically a gas oil, heavy crackedcycle oil, etc. In addition, alkylaromatic, olefins and naphthenes canbe conveniently isomerized by using the catalyst of the presentinvention. Likewise, pure hydrocarbons or substantially purehydrocarbons can be converted to more valuable products by using theacidic multimetallic catalyst of the present invention in any of thehydrocarbon conversion processes, known to the art, that use adual-function catalyst.

Since sulfur has a high affinity for cobalt at hydrocarbon conversionconditions, we have found that best results are achieved in theconversion of hydrocarbons with the instant acidic multimetalliccatalytic composite when the catalyst is used in a substantiallysulfur-free environment. This is particularly true in the catalyticreforming embodiment of the present invention. The expression"substantially sulfur-free enviroment" is intended to mean that thetotal amount (expresses as equivalent elemental sulfur) of sulfur orsulfur-containing compounds, which are capable of producing a metallicsulfide at the reaction conditions used, entering the reaction zonecontaining the instant catalyst from any source is continuouslymaintained at an amount equivalent to less than 10 wt. ppm, of thehydrocarbon charge stock, more preferably less than 5 wt. ppm, and mostpreferably less than 1 wt. ppm. Since in the ordinary operation of aconventional catalytic reforming process, wherein influent hydrogen isautogenously produced, the prime source for any sulfur entering thereforming zone is the hydrocarbon charge stock, maintaining the chargestock substantially free of sulfur is ordinarily sufficient to ensurethat the environment containing the catalyst is maintained in thesubstantially sulfur-free state. More specifically, since hydrogen is aby-product of the catalytic reforming process, ordinarily the inputhydrogen stream required for the process is obtained by recycling aportion of the hydrogen-rich stream recovered from the effluentwithdrawn from the reforming zone. In this typical situation, thisrecycle hydrogen stream will ordinarily be substantially free of sulfurif the charge stock is maintained free of sulfur. If autogenous hydrogenis not utilized, then of course the concept of the present inventionrequires that the input hydrogen stream be maintained substantiallysulfur-free; that is, less than 10 vol. ppm of H₂ S, preferably lessthan 5 vol. ppm and most preferably less than 1 vol. ppm.

The only other possible sources of sulfur that could interfere with theperformance of the instant catalyst are sulfur that is initiallycombined with the catalyst and/or with the plant hardware. As indicatedhereinbefore, a highly preferred feature of the present acidicmultimetallic catalyst is that it is maintained substantiallysulfur-free; therefore, sulfur released from the catalyst is not usuallya problem in the present process. Hardware sulfur is ordinarily notpresent in a new plant; it only becomes a problem when the presentprocess is to be implemented in a plant that has seen service with asulfur-containing feedstream. In this latter case, the preferredpractice of the present invention involves an initial pre-treatment ofthe sulfur-containing plant in order to remove substantially all of thedecomposable hardware sulfur therefrom. This can be easily accomplishedby any of the techniques for stripping sulfur from hardware known tothose in the art; for example, by the circulation of a substantiallysulfur-free hydrogen stream through the internals of the plant at arelatively high temperature of about 800° to about 1200°F. until the H₂S content of the effluent gas stream drops to a relatively low level --typically, less than 5 vol. ppm and preferably less than 2 vol. ppm. Insum, the preferred sulfur-free feature of the present invention requiresthat the total amount of detrimental sulfur entering the hydrocarbonconversion zone containing the hereinbefore described acidicmultimetallic catalyst must be continuously maintained at asubstantially low level; specifically, the amount of sulfur must be heldto a level equivalent to less than 10 wt. ppm, and preferably less than1 wt. ppm, of the feed.

In the case where the sulfur content of the feedstream for the presentprocess is greater than the amounts previously specified, it is, ofcourse, necessary to treat the charge stock in order to remove theundesired sulfur contaminants therefrom. This is easily accomplished byusing any one of the conventional catalytic pre-treatment methods suchas hydrorefining, hydrotreating, hydrodesulfurization, and the like toremove substantially all sulfurous, notrogenous and water-yieldingcontaminants from this feedstream. Ordinarily, this involves subjectingthe sulfur-containing feedstream to contact with a suitablesulfur-resistant hydrorefining catalyst in the presence of hydrogenunder conversion conditions selected to decompose sulfur contaminantscontained therein and form hydrogen sulfide. The hydrorefining catalysttypically comprises one or more of the oxides or sulfides of thetransition metals of Groups VI and VIII of the Periodic Table. Aparticularly preferred hydrorefining catalyst comprises a combination ofa metallic component from the iron group metals of Group VIII and of ametallic component of the Group VI transition metals combined with asuitable porous refractory support. Particularly good results have beenobtained when the iron group component is cobalt and/or nickel and theGroup VI transition metal is molybdenum or tungsten. The preferredsupport for this type of catalyst is a refractory inorganic oxide of thetype previously mentioned. For example, good results are obtained with ahydrorefining catalyst comprising cobalt oxide and molybdenum oxidesupported on a carrier material comprising alumina and silica. Theconditions utilized in this hydrorefining step are ordinarily selectedfrom the following ranges: a temperature of about 600° to about 950°F.,a pressure of about 500 to about 5000 psig., a liquid hourly spacevelocity of about 1 to about 20 hr. ⁻ ¹, and a hydrogen circulation rateof about 500 to about 10,000 standard cubic feet of hydrogen per barrelof charge. After this hydrorefining step, the hydrogen sulfide, ammoniaand water liberated therein, are then easily removed from the resultingpurified charge stock by conventional means such as a suitable strippingoperation. Specific hydrorefining conditions are selected from theranges given above as a function of the amounts and kinds of the sulfurcontaminants in the feedstream in order to produce a substantiallysulfur-free charge stock which is then charged to the process of thepresent invention.

In a reforming embodiment, it is generally preferred to utilize thenovel acidic multimetallic catalytic composite in a substantiallywater-free environment. Essential to the achievement of this conditionin the reforming zone is the control of the water level present in thecharge stock and the hydrogen stream which is being charged to the zone.Best results are ordinarily obtained when the total amount of waterentering the conversion zone from any source is held to a level lessthan 20 ppm and preferably less than 5 ppm expressed as weight ofequivalent water in the charge stock. As is demonstrated in theexamples, an especially preferred mode of operation of the instantcatalyst in a reforming process is under superdry conditions -- that is,with the total amount of water held to a level corresponding to lessthan 1 wt. ppm of water in the feed. In general, this can beaccomplished by careful control of the water present in the charge stockand in the hydrogen stream. The charge stock can be dried by using anysuitable drying means known to the art, such as a conventional solidadsorbent having a high selectivity for water, for instance, sodium orcalcium crystalline aluminosilicates, silica gel, activated alumina,molecular sieves, anhydrous calcium sulfate, high surface area sodiumand the like adsorbents. Similarly, the water content of the chargestock may be adjusted by suitable stripping operations in afractionation column or like device. And in some cases, a combination ofadsorbent drying and distillation drying may be used advantageously toeffect almost complete removal of water from the charge stock. In anespecially preferred mode of operation, the charge stock is dried to alevel corresponding to less than 5 wt. ppm of H₂ O equivalent. Ingeneral, it is preferred to maintain the hydrogen stream entering thehydrocarbon conversion zone at a level of about 10 vol. ppm of water orless and most preferably about 5 vol. ppm or less. If the water level inthe hydrogen stream is too high, drying of the same can be convenientlyaccomplished by contacting the hydrogen stream with a suitable desiccantsuch as those mentioned above.

In the reforming embodiment, an effluent stream is withdrawn from thereforming zone and passed through a cooling means to a separation zone,typically maintained at about 25° to 150°F., wherein a hydrogen-rich gasstream is separated from a high octane liquid product stream, commonlycallec an unstabilized reformate. When the water level in the hydrogenstream is outside the range previously specified, at least a portion ofthis hydrogen-rich gas stream is withdrawn from the separating zone andpassed through an adsorption zone containing an adsorbent selective forwater. The resultant substantially water-free hydrogen stream can thenbe recycled through suitable compressing means back to the reformingzone. The liquid phase from the separating zone is typically withdrawnand commonly treated in a fractionating system in order to adjust thebutane concentration, thereby controlling front-end volatility of theresulting reformate.

The operating conditions utilized in the numerous hydrocarbon conversionembodiments of the present invention are in general those customarilyused in the art for the particular reaction, or combination ofreactions, that is to be effected. For instance, alkylaromatic andparaffin isomerization conditions include: a temperature of about 32°F.to about 1000°F. and preferably from about 75° to about 600°F., apressure of atmospheric to about 100 atmospheres; a hydrogen tohydrocarbon mole ratio of about 0.5:1 to about 20:1 and an LHSV(calculated on the basis of equivalent liquid volume of the charge stockcontacted with the catalyst per hour divided by the volume of conversionzone containing catalyst) of about 0.2 hr..sup.⁻¹ to 10 hr. .sup.⁻¹.Dehydrogenation conditions include: a temperature of about 700 to about1250°F., a pressure of about 0.1 to about 10 atmospheres, a liquidhourly space velocity of about 1 to 40 hr. .sup.⁻¹ and a hydrogen tohydrocarbon mole ratio of about 1:1 to 20:1. Likewise, typicallyhydrocracking conditions include: a pressure of about 500 psig. to about3000 psig., a temperature of about 400°F. to about 900°F., an LHSV ofabout 0.1 hr..sup.⁻¹ to about 10 hr. .sup.⁻¹, and hydrogen circulationrates of about 100 to 10,000 SCF per barrel of charge.

In the reforming embodiment of the present invention, the pressureutilized is selected from the range of about 0 psig. to about 1000psig., with the preferred pressure being about 50 psig. to about 600psig. Particularly good results are obtained at low or moderatepressure; namely, a pressure of about 100 to 450 psig. In fact, it is asingular advantage of the present invention that it allows stableoperation at lower pressure than have heretofore been successfullyutilized in so-called "continuous" reforming systems (i.e. reforming forperiods of about 15 to about 200 or more barrels of charge per pound ofcatalyst without regeneration) with all platinum monometallic catalyst.In other words, the acidic multimetallic catalyst of the presentinvention allows the operation of a continuous reforming system to beconducted at lower pressure (i.e. 100 to about 350 psig.) for about thesame or better catalyst cycle life before regeneration as has beenheretofore realized with conventional monometallic catalysts at higherpressure (i.e. 400 to 600 psig.). On the other hand, the extraordinaryactivity and activity-stability characteristics of the catalyst of thepresent invention enables reforming conditions conducted at pressures of400 to 600 psig. to achieve substantially increased catalyst cycle lifebefore regeneration.

The temperature required for reforming with the instant catalyst ismarkedly lower than that required for a similar reforming operationusing a high quality catalyst of the prior art. This significant anddesirable feature of the present invention is a consequence of theextraordinary activity of the acidic multimetallic catalyst of thepresent invention for the octane-upgrading reactions that are preferablyinduced in a typical reforming operation. Hence, the present inventionrequires a temperature in the range of from about 800°F. to about1100°F. and preferably about 900°F. to about 1050°F. As is well known tothose skilled in the continuous reforming art, the initial selection ofthe temperature within this broad range is made primarily as a functionof the desired octane of the product reformate considering thecharacteristics of the charge stock and of the catalyst. Ordinarily, thetemperature then is thereafter slowly increased during the run tocompensate for the inevitable deactivation that occurs to provide aconstant octane product. Therefore, it is a feature of the presentinvention that not only is the initial temperature requirementsubstantially lower but also the rate at which the temperature isincreased in order to maintain a constant octane product issubstantially lower for the catalyst of the present invention than foran equivalent operation with a high quality reforming catalyst which ismanufactured in exactly the same manner as the catalyst of the presentinvention except for the inclusion of the cobalt, rhenium and tincomponents. Moreover, for the catalyst of the present invention, the C₅₊yield loss for a given temperature increase is substantially lower thanfor a high quality reforming catalyst of the prior art. Theextraordinary activity of the instant catalyst can be utilized in anumber of highly beneficial ways to enable increased performance of acatalytic reforming process relative to that obtained in a similaroperation with a monometallic or bimetallic catalyst of the prior art,some of these are: (1) Octane number of C₅₊ product can be substantiallyincreased without sacrificing catalyst run length. (2) The duration ofthe process operation (i.e. catalyst run length or cycle life) beforeregeneration becomes necessary can be significantly increased. (3) C₅₊yield can be increased by lowering average reactor pressure with nochange in catalyst run length. (4) Investment costs can be loweredwithout any sacrifice in cycle life by lowering recycle gas requirementsthereby saving on capital cost for compressor capacity or by loweringinitial catalyst loading requirements thereby saving on cost of catalystand on capital cost of the reactors. (5) Throughput can be increasedsharply at no sacrifice in catalyst cycle life if sufficient heatercapacity is available.

The reforming embodiment of the present invention also typicallyutilizes sufficient hydrogen to provide an amount of about 1 to about 20moles of hydrogen per mole of hydrocarbon entering the reforming zone,with excellent results being obtained when about 2 to about 6 moles ofhydrogen are used per mole of hydrocarbon. Likewise, the liquid hourlyspace velocity (LHSV) used in reforming is selected from the range ofabout 0.1 to about 10.sup.⁻¹, with a value in the range of about 1 toabout 5 hr..sup.⁻¹ being preferred. In fact, it is a feature of thepresent invention that it allows operations to be conducted at higherLHSV than normally can be stably achieved in a continuous reformingprocess with a high quality reforming catalyst of the prior art. Thislast feature is of immense economic significance because it allows acontinuous reforming process to operate at the same throughput levelwith less catalyst inventory or at greatly increased throughput levelwith the same catalyst inventory than that heretofore used withconventional reformig catalysts at no sacrifice in catalyst life beforeregeneration.

The following examples are given to illustrate further the preparationof the acidic multimetallic catalytic composite of the present inventionand the use thereof in the conversion of hydrocarbons. It is understoodthat the examples are intended to be illustrative rather thanrestrictive.

EXAMPLE I

A tin-containing alumina carrier material comprising 1/16 inch sphereswas prepared by: forming an aluminum hydroxyl chloride sol by dissolvingsubstantially pure aluminum pellets in a hydrochloric acid solution,adding stannic chloride to the resulting sol in an amount selected toresult in a finished catalyst containing about 0.15 wt. % tin, addinghexamethylenetetramine to the resulting tin-containing alumina solgelling the resulting solution by dropping it into an oil bath to formspherical particles of aluminum- and tin-containing hydrogel, aging andwashing the resulting particles and finally drying and calcining theaged and washed particles to form spherical particles of gamma-aluminacontaining a uniform dispersion of about 0.15 wt. % tin in the form oftin oxide and about 0.3 wt. % combined chloride. Additional details asto this method of preparing the preferred gamma-alumina carrier materialare given in the teachings of U.S Pat. No. 2,620,314.

An acidic aqueous impregnation solution containing chloroplatinic acid,perrhenic acid, cobaltous chloride, and hydrogen chloride was thenprepared. The tin-containing alumina carrier material was thereafteradmixed with the impregnation solution. The amount of reagent containedin this impregnation solution was calculated to result in a finalcomposite containing, on an elemental basis, 0.375 wt. % platinum, 0.375wt. % rhenium, and 0.5 wt. % cobalt. In order to insure uniformdispersion of the metallic components throughout the carrier material,the amount of hydrochloric acid used was about 3 wt. % of the aluminaparticles. This impregnation step was performed by adding the carriermaterial particles to the impregnation mixture with constant agitation.In addition, the volume of the solution was approximately the same asthe void volume of the carrier material particles. The impregnationmixture was maintained in contact with the carrier material particlesfor a period of about 1/2 to about 3 hours at a temperature of about70°F. Thereafter, the temperature of the impregnation mixture was raisedto about 225°F. and the excess solution was evaporated in a period ofabout 1 hour. The resulting dried impregnated particles were thensubjected to an oxidation treatment in a dry air stream at a temperatureof about 975°F. and a GHSV of about 500 hr..sup.⁻¹ for about 1/2 hour.This oxidation step was designed to convert substantially all of themetallic ingredients to the corresponding oxide forms. The resultingoxidized spheres were subsequently contacted in a halogen treating stepwith an air stream containing H₂ O and HCl in a mole ratio of about 30:1for about 2 hours at 975°F. and a GHSV of about 500 hr..sup.⁻¹ in orderto adjust the halogen content of the catalyst particles to a value ofabout 0.88 wt. %. The halogen-treated spheres were thereafter subjectedto a second oxidation step with a dry air stream at 975°F. and a GHSV of500 hr. .sup.⁻¹ for an additional period of about 1/2 hour.

The oxidized and halogen-treated catalyst particles were then subjectedto a dry prereduction treatment, designed to reduce the platinumcomponent to the elemental state while maintaining the tin component inpositive oxidation state, by contacting it for about 1 hour with asubstantially hydrocarbon-free dry hydrogen stream containing less than5 vol. ppm H₂ O at a temperature of about 1050°F., a pressure slightlyabove atmospheric, and a flow rate of the hydrogen stream through thecatalyst particles corresponding to a gas hourly space velocity of about400 hr.⁻¹.

Examination of a sample of a catalyst of the present type afterpreparation as outlined above by electron spin resonance techniquesindicated that substantially all of the platinum component had beenreduced whereas substantially all of the tin component remained in thetin oxide state. Likewise for a cobalt-containing catalyst prepared bythis procedure controlled reduction experiments along with additionalevidence from electron spin resonance established that at the completionof this reduction step, substantially all of the cobalt component was ina readily reducible oxide form. Studies of the cobalt and rheniumcrystallites contained in catalysts of the present kind, after they havebeen exposed to hydrocarbons during the subsequently described reformingoperation, provided evidence that substantially all of the cobalt andrhenium components were reduced to the corresponding elemental metallicstate at the reforming conditions utilized.

A sample of the resulting reduced catalyst particles was analyzed andfound to contain, on an elemental basis, about 0.375 wt. % platinum,about 0.375 wt. % rhenium, about 0.5 wt. % cobalt, about 0.15 wt. % tin,and about 0.88 wt. % chloride. This corresponds to an atomic ratio oftin to platinum of 0.65:1, of rhenium to platinum of 1.05:1 and to anatomic ratio of cobalt to platinum of 4.4:1. The resulting acidicmultimetallic catalyst is hereinafter referred to as catalyst "A".

EXAMPLE II

In order to compare the novel acidic multimetallic catalytic compositeof the present invention with leading bimetallic catalytic composites ofthe prior art in a manner calculated to bring out the beneficialinteraction of a combination of cobalt, rhenium, and tin components on aplatinum-containing catalyst, a comparison test was made between theacidic multimetallic catalyst of the present invention which wasprepared in Example I (i.e. catalyst "A") and superior bimetallicreforming catalysts of the prior art which, in the first case, containeda combination of platinum and tin as its hydrogenation-dehydrogenationcomponent and, in the second case, contained a combination of platinumand rhenium as the dehydrogenation-hydrogenation component. The firstcontrol catalyst was a combination of a platinum component, a tincomponent and a chloride component with a gamma-alumina carrier materialin amounts sufficient to result in the final catalyst containing about0.6 wt. % platinum, about 0.5 wt % tin, and about 1.19 wt. % chloride.This first control catalyst is hereinafter referred to as catalyst "B".The second control catalyst was a combination of a platinum component, arhenium component, and a chloride component with a gamma-alumina carriermaterial in amounts sufficient to result in the final catalystcontaining 0.375 wt. % platinum, 0.375 wt. % rhenium, and 0.87 wt. %chloride. This second control catalyst is designated herein as catalyst"C". Catalysts "b" and "C" were prepared by methods analogous to thatset forth in Example I with appropriate modifications to result in thestated compositions.

These catalysts were then separately subjected to a high stressaccelerated catalytic reforming evaluation test designed to determine ina relatively short period of time their relative activity, selectivity,and stability characteristics in a process for reforming a relativelylow-octane gasoline fraction. In all of the tests the same charge stockwas utilized and its pertinent characteristics are set forth in Table I.It is to be noted that in all cases the test was conducted undersubstantially water-free conditions with the only significant source ofwater being the 14 to 18 wt. ppm present in the charge stock. Likewise,it is to be observed that the tests were performed under substantiallysulfur-free conditions with the only sulfur input into the plant beingthe 0.1 ppm sulfur contained in the charge stock.

                  TABLE I                                                         ______________________________________                                        Analysis of Charge Stock                                                      ______________________________________                                        Gravity, °API at 50° F.                                                              59.7                                                     Distillation Profile, ° F.                                              Initial Boiling Point                                                                             178                                                        5% Boiling Point   199                                                       10% Boiling Point   210                                                       30% Boiling Point   232                                                       50% Boiling Point   244                                                       70% Boiling Point   286                                                       90% Boiling Point   320                                                       95% Boiling Point   336                                                       End Boiling Point   376                                                      Chloride, wt. ppm    0.35                                                     Nitrogen, wt. ppm    0.2                                                      Sulfur, wt. ppm      0.1                                                      Water, wt. ppm       14-18                                                    Octane Number, F-1 Clear                                                                           41.0                                                     Paraffins, vol. %    67                                                       Naphthenes, vol. %   21.2                                                     Aromatics, vol. %    11.8                                                     ______________________________________                                    

This accelerated reforming test was specifically designed to determinein a vary short period of time whether the catalyst being evaluated hassuperior characteristics for use in a high severity reforming operation.Each run consisted of a series of evaluation periods of 24 hours, eachof these periods comprised a 12 hour line-out period followed by a 12hour test period during which the C₅₊ product reformate from the plantwas collected and analyzed. The test runs were performed at identicalconditions which comprised a liquid hourly space velocity (LHSV) of 3.0hr..sup.⁻¹, a pressure of 300 psig., a 10:1 gas to oil ratio, and aninlet reactor temperature which was continuously adjusted throughout thetest in order to achieve and maintain a C₅ ⁻ target octane of 100 F-1clear.

The tests were performed in a pilot plant scale reforming unitcomprising a reactor containing a fixed bed of the catalyst undergoingevaluation, a hydrogen separation zone, a debutanizer column, andsuitable heating means, pumping means, condensing means, compressingmeans, and the like conventional equipment. The flow scheme utilized inthis plant involves commingling a hydrogen recycle stream with thecharge stock and heating mixture is then passed downflow into a reactorcontaining the catalyst undergoing evaluation as a stationary bed. Aneffluent stream is then withdrawn from the bottom of the reactor, cooledto about 55°F. and passed to a gas-liquid separation zone wherein ahydrogen-rich gaseous phase separates from a liquid hydrocarbon phase. Aportion of the gaseous phase is then continuously passed through a highsurface area sodium scrubber and the resulting substantially water-freeand sulfur-free hydrogen stream is returned to the reactor in order tosupply the hydrogen recycle stream. The excess gaseous phase from theseparation zone is recovered as the hydrogen-conntaining product stream(commonly called "excess recycle gas"). The liquid phase from theseparation zone is withdrawn therefrom and passed to a debutanizercolumn wherein light ends (i.e. C₁ to C₄) are taken overhead asdebutanizer gas and a C₅₊ reformate stream recovered as the principalbottom product.

The results of the separate tests performed on a particularly preferredcatalyst of the present invention, catalyst "A", and the controlcatalysts, catalyst "B" and "C", are presented for each test period inTable II in terms of inlet temperature to the reactor in °F. necessaryto achieve the target octane level and the amount of C₅₊ reformaterecovered expressed as liquid vol. % (LV%) of the charge stock.

                                      TABLE II                                    __________________________________________________________________________    Results of Accelerated Reforming Test                                         CATALYST "A"    CATALYST "B"                                                                             CATALYST "C"                                       Period                                                                            T, ° F                                                                       C.sub.5 +, LV%                                                                      T, ° F                                                                      C.sub.5 +, LV%                                                                      T, ° F                                                                        C.sub.5 +, LV%                              __________________________________________________________________________     1  961.0 66.75  994.5                                                                             72.1  993.5  68.92                                        2  966.5 68.16 1000.0                                                                             71.3  997.0  69.32                                        3  971.0 --    1004.0                                                                             --    1000.0 --                                           4  970.5 70.51 1002.5                                                                             72.4  994.0  70.73                                        5  973.5 --    1006.0                                                                             --    993.0  --                                           6  972.5 70.13 1006.0                                                                             71.1  995.0  70.67                                        7  975.0 --    1007.0                                                                             --    996.0  --                                           8  978.0 68.95 1010.0                                                                             71.8  996.5  69.33                                        9  979.5 --    1011.5                                                                             --    995.0  --                                          10  982   70.50 1015.5                                                                             70.1  996.5  68.52                                       11  985   --    1017.5                                                                             --    999.0  --                                          12  988.5 69.47 1017.0                                                                             71.3  1000.5 65.76                                       __________________________________________________________________________

Referring now to the results of the comparison test presented in TableII. it is evident that the principal effect of using a combination ofcobalt, rhenium, and tin to promote a platinum-containing catalyst,relative to the results observed using rhenium or tin as a solepromoter, is a substantial increase in activity for the multimetalliccatalyst of the present invention, which is unexpectedly achieved whileretaining exceptionally good selectivity. That is, the data presented inTable II clearly indicates that the acidic multimetallic catalyst of thepresent invention is markedly superior in activity to both controlcatalysts in a high severity reforming process. As was pointed out indetail hereinbefore, a good measure of activity for a reforming catalystis the inlet temperature to the reactor which is required to make targetoctane and the data presented in Table II on this variable clearly showsthat catalyst "A" was signficantly more active than catalysts "B" and"C". The activity advantage that catalyst "A" manifests is consistentlyequal to or better than about 30°F., relative to catalyst "B" and about12°F., relative to catalyst "C", measured in terms of inlet reactortemperature. This is truly outstanding when one realizes that as a ruleof thumb, the rate of a reaction ordinarily doubles for every 18° to20°F. increase in reactor temperature. Thus, these activity differencesmean that the catalyst of the present invention is consistently three orfour times as active as control catalyst "B" and about 1 to about 2times as active as control catalyst "C". A specific example of thisactivity advantage can be obtained by looking at the data for period 12of the test (i.e. 288 hours into the test), at this point, catalyst "A"required an inlet temperature of 988.5 in order to make octane whichstand in sharp contrast to the 1017.0 requirement of catalyst "B" and100.05 requirement of catalyst "C" at the same point in the run. Thesesignificant differences in temperature requirement for octane isimpressive evidence of the ability of the catalyst of the presentinvention to materially accelerate the rate of the involved reformingreaction without materially changing the C₅₊ yield. Thus, the dataclearly shows that the composite of the present invention wasconsistently more active than both control catalysts. However, activityis only one of the necessary characteristics needed in order for acatalyst to demonstrate superiority. Activity characteristics must becoupled with superior or equivalent selectivity characteristics in orderto demonstrate improved performance for the duration of this test.selectivity is measured directly by C₅₊ yield and the data presented inTable II clearly indicates that catalyst "A" uniformly produced yieldsequivalent to those for catalysts "B" and "C". (It is to be noted thatthe dashes in Table II represent periods where the relevant analyses ofthe product streams were not made.) On the other hand, good stabilitycharacteristics are shown by the rate of change of the activity andselectivity parameters as was explained hereinbefore, and on this basisthe incremental change in temperature required to maintain octane and inC₅₊ yield exhibited in Table II clearly shows acceptable stability forthe catalyst of the present invention.

In summary, it is clear from the data presented in Table II that acombination of cobalt, rhenium, and tin is an efficient and effectivepromoter for a platinum-containing acidic reforming catalyst in a highseverity reforming operation.

EXAMPLE III

In order to study the effect of a superdry operation on the performanceof the acidic multimetallic catalyst of the present invention in areforming operation, a comparison was made between a run with catalyst"A" operated under superdry conditions (the total amount of equivalentwater changed to the reforming zone held at a level less than 1 wt. ppmof the feed) and a run with catalyst "A" operated under substantiallywater-free conditions (14 to 18 wt. ppm water charged to the reformingzone).

The charge stock, condition, and test procedure used were the same asdescribed in Example II except for the water level in feed difference.

The results of the comparison tests are presented in Table III in thesame terms as used in Table II.

                  TABLE III                                                       ______________________________________                                        Results of Water Level Study                                                  Superdry (<1 wt. ppm)                                                                              Dry (14-18 wt. ppm)                                      Period  T, °F                                                                            C.sub.5 +, LV%                                                                           T, °F                                                                          C.sub.5 +, LV%                           ______________________________________                                         1      964.0     --         961.0   66.75                                     2      963.5     68.73      966.5   68.16                                     3      962.0     --         971.0   --                                        4      961.0     68.48      970.5   70.51                                     5      960.0     --         973.5   --                                        6      960.0     68.33      972.5   70.13                                     7      960.5     --         975.0   --                                        8      961.5     66.81      978.0   68.95                                     9      963.0     --         979.5   --                                       10      963.0     67.36      982.0   70.50                                    11      963.5     --         985.0   --                                       12      964.0     --         988.5   69.47                                    ______________________________________                                    

Inspection of the data presented in Table III reveals that the use of asuperdry operation enables a remarkable and surprising improvement inthe activity-stability of the multimetallic catalyst of the presentinvention.

It is intended to cover by the following claims, all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in the hydrocarbonconversion art or in the catalyst formulation art.

We claim as our invention:
 1. A process for converting a hydrocarbonwhich comprises contacting the hydrocarbon at hydrocarbon conversionconditions with an acidic catalytic composite comprising a porouscarrier material containing, on an elemental basis, about 0.01 to about2 wt. % platinum group metal, about 0.01 to about 2 wt. % rhenium, about0.05 to about 5 wt. % cobalt, about 0.01 to about 5 wt. % tin, and about0.1 to about 3.5 wt. % halogen, wherein the platinum group metal,rhenium, cobalt, and tin are uniformly dispersed throughout the porouscarrier material, wherein the average crystallite size of the cobalt andtin is less than 100 Angstroms in maximum dimension whereinsubstantially all of the platinum group metal is present in theelemental metallic state, wherein substantially all of the tin ispresent in an oxidation state above that of the elemental metal, andwherein substantially all of the cobalt and rhenium are present in thecorresponding elemental metallic state or in a state which is reducibleto the corresponding elemental metallic state under hydrocarbonconversion conditions or in a mixture of these states.
 2. A process asdefined in claim 1 wherein the platinum group metal is platinum.
 3. Aprocess as defined in claim 1 wherein the platinum group metal isiridium.
 4. A process as defined in claim 1 wherein the platinum groupmetal is palladium.
 5. A process as defined in claim 1 wherein theplatinum group metal is rhodium.
 6. A process as defined in claim 1wherein the porous carrier material is a refractory inorganic oxide. 7.A process as defined in claim 6 wherein the refractory inorganic oxideis alumina.
 8. A process as defined in claim 1 wherein the halogen iscombined chloride.
 9. A process as defined in claim 1 wherein the atomicratio of rhenium to platinum group metal contained in the composite is0.05:1 to 10:1.
 10. A process as defined in claim 1 wherein the atomicratio of tin to platinum group metal contained in the composite is about0.1:1 to about 13:1.
 11. A process as defined in claim 1 wherein theatomic ratio of cobalt to platinum group metal contained in thecomposite is about 0.1:1 to about 66:1.
 12. A process as defined inclaim 1 wherein substantially all of the cobalt and rhenium contained inthe composite are present in the corresponding elemental metallic stateafter the process is started-up and lined-out at the hydrocarbonconversion conditions.
 13. A process as defined in claim 1 whereinsubstantially all of the tin is present in the catalytic composite astin oxide.
 14. A process as defined in claim 1 wherein the compositecontains about 0.05 to about 1 wt. % platinum, about 0.05 to about 1 wt.% rhenium, about 0.10 to about 2.5 wt. % cobalt, about 0.05 to about 1wt. % tin, and about 0.5 to about 1.5 wt. % halogen.
 15. A process asdefined in claim 1 wherein the contacting of the hydrocarbon with thecatalytic composite is performed in the presence of hydrogen.
 16. Aprocess as defined in claim 1 wherein the type of hydrocarbon conversionis catalytic reforming of a gasoline fraction to produce a high octanereformate, wherein the hydrocarbon is contained in the gasolinefraction, wherein the contacting is performed in the presence ofhydrogen, and wherein the hydrocarbon is contained in the gasolinefraction, wherein the contacting is performed in the presence ofhydrogen, and wherein the hydrocarbon conversion conditions arereforming conditions.
 17. A process as defined in claim 16 wherein thereforming conditions include a temperature of about 800° to about1100°F., a pressure of about 0 to about 1000 psig., a liquid hourlyspace velocity of about 0.1 to about 10 hr.⁻ ¹, and a mole ratio ofhydrogen to hydrocarbon of about 1:1 to about 20:1.
 18. A process asdefined in claim 16 wherein the contacting is performed in asubstantially water-free environment.
 19. A process as defined in claim16 wherein the contacting is performed under super dry conditions.
 20. Aprocess as defined in claim 16 wherein the reforming conditions includea pressure of about 100 to about 450 psig.
 21. A process as defined inclaim 16 wherein the contacting is performed in a substantiallysulfur-free environment.
 22. A process as defined in claim 14 whereinthe type of hydrocarbon conversion is catalytic reforming of a gasolinefraction to produce a high octane reformate, wherein the hydrocarbon iscontained in the gasoline fraction, wherein the contacting is performedin the presence of hydrogen and wherein the hydrocarbon conversionconditions are reforming conditions.
 23. An acidic catalytic compositecomprising a porous carrier material containing, on an elemental basis,about 0.01 to about 2 wt. % platinum group metal, about 0.01 to about 2wt. % rhenium, about 0.05 to about 5 wt. % cobalt, about 0.01 to about 5wt. % tin, and about 0.1 to about 3.5 wt. % halogen, wherein theplatinum group metal, rhenium, cobalt, and tin are uniformly dispersedthroughout the porous carrier material wherein the average crystallitesize of the cobalt and tin is less than 100 Angstroms in maximumdimension, wherein substantially all of the platinum group metal ispresent in the elemental metallic state, wherein substantially all ofthe tin is present in an oxidation state above that of the elementalmetal, and wherein substantially all of the cobalt and rhenium arepresent in the corresponding elemental metallic state or in a statewhich is reducible to the corresponding elemental metallic state underhydrocarbon conversion conditions or in a mixture of these states.